Return The File Extension of a File

So this little method will return the file extension of a file. That is, it will look for the dot (.) in a filename and return the remaining characters after it.

Notice that it makes sure it's a file and not a directory.

/**
     * Returns the extension of a file
     *
     * @param filename the name of the file
     * @return the extension of the filename
     */
    public static String getExtension(String filename) {
        String ext = null;

        File file = new File(filename);
        if (file.exists() && file.isFile()) {
            ext = filename.substring(filename.lastIndexOf(".") + 1);
        }

        return ext;
    }

Pretty simple no? Yeah that's what I was thinking.

You can easily put this in a FileUtils class that you might be building. It could come in handy.

Please remember that the file extension does not dictate what the file type is. It's just an extension.